This invention relates to flow control, and, more particularly to the control of fluid flow for in-line applications.
In many situations it is necessary to control the in-line flow of fluids such as liquids and gases. A common device for that purpose is a variable clamp. It functions by squeezing the line to constrict the opening through which the fluid passes. It requires that the line have sufficient resiliency to recover when the clamping pressure is removed. The objection to the clamping technique is that it cannot be used with relatively rigid conduits. In addition, the control that is exercised over fluid flow by clamping is imprecise.
Attempts have been made to overcome the foregoing difficulties by the use of valves which are placed in the line. Such valves tend to be complex and expensive. They are usually imprecise in their operation. They frequently provide an initial flow surge and are characterized by dead space. In addition they tend to drift and do not have a stable set position. The principal objection however is that they usually provide imprecise control over flow and are not able to provide flow control over a wide range. Typical flow control devices of the prior art are those illustrated in the following patents:
______________________________________ Patent No. Issued Inventor ______________________________________ 4,073,314 2/14/78 Speelman, et al. 3,943,969 3/16/76 Rubin, et al. 3,659,573 5/2/72 Bennett 3,503,418 3/31/70 Petrucci, et al. 3,255,774 6/14/66 Gallagher, et al. ______________________________________
Accordingly, it is an object of the invention to facilitate the control of fluid flow. A related object is to facilitate the control of fluid flow for in-line applications.
A further object of the invention is to overcome the difficulties associated with prior flow control valves. A related object is to avoid the difficulties associated with clamping type valves.
Still another object of the invention is to avoid initial flow surge in flow control valves, as well as a reduction in dead space in flow control valves.
Yet another object of the invention is to provide a flow control valve with fine metering as well as repeatable flow adjustments. Still another object is to achieve stable locking with reduced drift. A further object is to provide a comparatively broad range of flow control adjustment.